Is Class A the best design? Look at it this way: no preamplifier designer would ever build anything other than Class A.
This statement says it all, if a preamp was a/b it wouldn’t sound very good, all decent preamps are class A.
It’s the same for Class A amps even more so, but you have to cop the negatives, heat, powersupply ability, size, weight, and power consumption.
All these negatives have nothing to do with poor sound quality, if fact it’s the opposite, Class A done "right" is superior to any a/b, b, d, h etc etc
Cheers George